Elastic supports of the above type are known which generally comprise a base element of rigid or semirigid material, a padding or filling element made of a resilient material, usually polyurethane resin and/or gel, and a sheet cover element, usually of imitation leather or the like, which is designed to contact a seated user.
Various processes for forming such types of supports are also known, which are all intended to join together the above elements, in one or more steps, to form a comfortable and resistant final product.
European patent EP-B1-0653279, by the applicant hereof, discloses a process for forming supports of the above mentioned type, which uses a male—female mold, in which the various elements are successively laid.
Particularly, the female mold, which has a negative forming cavity conformed to the shape of the top surface of the support to be formed, first receives the cover element, with the bottom surface facing upwards. Such female mold further has vacuum means for the element to be laid with no surface fold or unevenness.
The resilient element is then placed, still in the liquid state, on the cover element. Such resilient element contains blowing agents, usually CFC gases, which will provide the typical highly porous honeycomb structure of such types of padding.
Then the mold is closed, by coupling the male part, with the base element thereon, to the female part. The structure is left in the mold, which is adequately heated, for a sufficient time and at a sufficient temperature to allow resin expansion and curing of the resin and/or gel. In this step, the resin and/or gel are “bonded” to the base element and the cover element, thanks to chemical and/or physical interaction of such elements. In the last step of the process, the final product is finished and all flashes of excess material are trimmed, typically by a manual operation.
Such prior art process has the apparent drawback that the supports formed thereby have a water-pervious peripheral edge, and allow water to penetrate the structure, thereby causing cover element removal with time. This is caused by the high porosity of the elastic resin, which is naturally subjected to liquid absorption. Furthermore, if the support contains gel, water contact has to be necessarily avoided, to prevent gel decomposition. This problem would be also dramatically aggravated by an imperfect finishing step, which is likely to occur, considering it is a manual operation.
WO2005/051629, in the name of the same applicant, discloses a process for making integral elastic supports of the above type, including a step in which an annular sealing rim is formed on the base element, to create a preferential thickening area for the expandable resin, to further facilitate the succeeding manual support finishing step.
While this solution meets the intended requirements, it does not wholly solve the problem of water penetrating the filling element. This is caused by the sealing bead being still exposed to weather between the base and the padding.
No solution against liquid penetration at the edge portions of elastic elements having a relatively highly porous filling element has been provided heretofore in prior art.
Also, both the above solutions have other apparent drawbacks.
First, when the CFC-containing resin thickens on the cover element, a layer (known as “chemical skin”) is actually formed therebetween, which makes the support uncomfortable for use and affects resin elasticity.
Furthermore, these prior art processes use an excessive amount of resin, most of it being required to form the sealing bead. This waste is further aggravated by the need of using a highly porous resin in an area that has to be as waterproof as possible, for the reasons stated above.
Finally, the use of CFC blowing agents is highly hazardous for the environment.